John,
My favorite mode with the stock coil was C/J. The settings i used were killer on coins. i got nickels at 8 inches. Coin Mode, Gain on 9, disc on 2 groung to track trigger in center and threshold just below sound. All the rings I found that I posted earlier where found with the stock coil using this set up. Coin mode works great. However I found relic mode to do better in rusted iron trash. Hit an old home site where and old house had been pushed down. Alot of nails and big iron, ground read in the 70's just a rough place to look. I switched to relic mode set the disc on 4 trigger forward went slow and dug only repeating high tones and pulled out a 1916 merc dime(back obliterated) a 1909 wheatie a 1928 buff nickel and 28 more wheats and a 1920-1930 eagle button. The stock was the only coil I had for 8 months, I had no choice but to use it every where and it will do a good job. But to learn the machine I would say yes , learn the coin mode at a moderate gain setting and once you get the hang of what it will do and what it is telling you than play with more gain and the other modes, it will seem like a different machine in each mode, and actually it is, that is the great thing about the MXT, it is one of the most versatile machines out there and it will find treasure with the best of them.
Ray